支持mysql information_schema 元数据返回

src/main/java/io/mycat/server/handler/MysqlInformationSchemaHandler.java

@@ -0,0 +1,86 @@
+package io.mycat.server.handler;
+
+import java.nio.ByteBuffer;
+
+import io.mycat.backend.mysql.PacketUtil;
+import io.mycat.config.Fields;
+import io.mycat.net.mysql.EOFPacket;
+import io.mycat.net.mysql.FieldPacket;
+import io.mycat.net.mysql.OkPacket;
+import io.mycat.net.mysql.ResultSetHeaderPacket;
+import io.mycat.server.ServerConnection;
+import io.mycat.server.util.SchemaUtil;
+
+
+/**
+ * 对 PhpAdmin's 控制台操作进行支持 
+ * 
+ * 如：SELECT * FROM information_schema.CHARACTER_SETS 等相关语句进行模拟返回
+ * 
+ * @author zhuam
+ *
+ */
+public class MysqlInformationSchemaHandler {
+
+	/**
+	 * 写入数据包
+	 * @param field_count
+	 * @param fields
+	 * @param c
+	 */
+	private static void doWrite(int field_count, FieldPacket[] fields, ServerConnection c) {
+
+		ByteBuffer buffer = c.allocate();
+
+		// write header
+		ResultSetHeaderPacket header = PacketUtil.getHeader(field_count);
+		byte packetId = header.packetId;
+		buffer = header.write(buffer, c, true);
+
+		// write fields
+		for (FieldPacket field : fields) {
+			field.packetId = ++packetId;
+			buffer = field.write(buffer, c, true);
+		}
+
+		// write eof
+		EOFPacket eof = new EOFPacket();
+		eof.packetId = ++packetId;
+		buffer = eof.write(buffer, c, true);
+
+		// write last eof
+		EOFPacket lastEof = new EOFPacket();
+		lastEof.packetId = ++packetId;
+		buffer = lastEof.write(buffer, c, true);
+
+		// post write
+		c.write(buffer);
+
+	}
+
+	public static void handle(String sql, ServerConnection c) {
+
+		SchemaUtil.SchemaInfo schemaInfo = SchemaUtil.parseSchema(sql);
+		if ( schemaInfo != null ) {
+
+			if ( schemaInfo.table.toUpperCase().equals("CHARACTER_SETS") ) {
+
+				//模拟列头
+				int field_count = 4;
+			    FieldPacket[] fields = new FieldPacket[field_count];
+			    fields[0] = PacketUtil.getField("CHARACTER_SET_NAME", Fields.FIELD_TYPE_VAR_STRING);
+				fields[1] = PacketUtil.getField("DEFAULT_COLLATE_NAME", Fields.FIELD_TYPE_VAR_STRING);
+			    fields[2] = PacketUtil.getField("DESCRIPTION", Fields.FIELD_TYPE_VAR_STRING);
+				fields[3] = PacketUtil.getField("MAXLEN", Fields.FIELD_TYPE_LONG);
+
+				doWrite(field_count, fields, c);				
+
+			} else {
+				c.write(c.writeToBuffer(OkPacket.OK, c.allocate()));
+			}			
+
+		} else {
+			c.write(c.writeToBuffer(OkPacket.OK, c.allocate()));
+		}		
+	}
+}